1. Field of the Invention
The present invention relates to a disk array apparatus, a computer-readable recording medium having a disk array apparatus control program recorded thereon, and a disk array apparatus control method.
2. Description of the Related Art
Conventionally, data input/output devices have a disk mounted thereon and control access from an upper-level device to the disk. More specifically, a data input/output device reads out requested data from a disk when it is required to read out the data by an upper-level device and writes data to the disk when it is required to write the data. Among data input/output devices, disk array apparatuses are designed with disk redundancy so as not to lose data even if one disk fails.
More specifically, a disk array apparatus has a plurality of disks constituting a RAID (Redundant Arrays of Inexpensive Disks) group mounted thereon and controls access from an upper-level device to each of the disks. The maximum storage capacities of disk array apparatuses have recently increased with an increase in the storage capacities of disks up to the order of petabytes. The number of disks constituting a RAID group has increased in proportion to the increase in the storage capacities of disks.
If, as described above, the number of disks mounted on a disk array apparatus increases, the likelihood of disk failures also increases. For this reason, periodic medium check and status monitoring are generally performed on disks mounted on a disk array apparatus. The constant monitoring of the statuses of the disks is aimed at early detection of a disk with a medium abnormality or driving system abnormality and normalization of the status.
The above-described conventional technique suffers from the problem of an inability to appropriately detect a performance abnormality (a fault which causes a disk to have an abnormal performance value). That is, although the conventional technique is capable of detecting a medium abnormality and a driving system abnormality, as described above, it is incapable of detecting a performance abnormality. This is because a disk can operate with performance of a level which is not recognized as abnormal by an upper-level device, even though the performance of a disk with a performance abnormality is poorer than one under normal conditions, since a timeout for processing or the like does not occur. Although a disk with a performance abnormality operates without causing a so-called abnormality, if a data access delay due to the performance abnormality occurs, an event which interferes with normal functioning of a system (e.g., a process which has conventionally been completed within a prescribed time fails to be completed within the prescribed time) may occur. For this reason, it is necessary to detect a disk with a performance abnormality.